On Sunday, Mays' lawyer, Adam Nemann, also said he planned to file at least two motions including a change of venue "given its publicity and what we perceive as threats to individuals, perhaps witnesses, and also defendants and even defense counsel."

Media attention and an explosion of online postings about the case are part of the reason, according to Nemann.

"We're concerned about safety issues at this point," he added.

On Sunday, Tierney would not discuss whether there are any alleged threats.

"The investigation is ongoing and it includes all aspects of the case including evidence put out in social media, Tierney told CNN.

Mays and Richmond are each charged with raping a 16-year-old girl during late-night partying and drinking last August, according to prosecutors.

CNN is not identifying the girl, who is a juvenile, in accordance with its policy not to release the names of alleged rape victims.

"She was unresponsive, not in a position of consent, and they knew about it, and let's be clear, they knew she was drunk," special prosecutor Marianne Hemmeter told a judge at probable cause hearing last October.

A judge from Cincinnati is hearing the case after a local judge recused himself to avoid an appearance of conflict of interest.

Police Chief William McCafferty says many people in the small eastern Ohio town know someone who may have a connection to the case.

Often trials are granted a change of venue because of fear of a tainted jury pool. This trial is a bench trial, meaning the judge will determine the teens' fate.

But defense attorney Nemann said he has another reason to ask for the change. He plans to tell the judge his case may be hamstrung by hesitant witnesses.

"I'm concerned about whether or not the case should be tried in this area. Perhaps the fact that it is in the Steubenville area is going to prohibit certain people from wanting to come forward and testify," Nemann said.

Some potential witnesses who attended the parties where the alleged sexual assaults occurred are refusing to talk with his defense team, the lawyer said. He would not say how many witnesses.

The motions will be filed under seal, Nemann said.

Lawyers for both defendants have said their clients are not guilty of the charges.

"We deny the accusations completely. We deny the lack of consent. We deny that there was sexual activity. We deny that there was a rape. And we steadfastly maintain that," Nemann told CNN.